const log=(arg1:Object,methodName:String,decorator:PropertyDescriptor)=>{
    const method=decorator.value
    decorator.value=()=>{
       console.log('开始打印日志了');
       method()
       console.log('结束打印日志了');  
    }    
}
class MyClss{
    @log
    render(){
        console.log('用于页面渲染的方法');
    }
}
let mc=new MyClss()
mc.render()
